The present invention relates to a spraying apparatus and more particularly to an improved spray gun adapted for spraying liquidous mixtures such as cementitious slurries, ceiling acoustic or wall texture by means of compressed air.
The speed and convenience as well as the quality of the work product afforded by the application of such mixtures by spraying has generally caused more laborious manual methods to be supplanted. Furthermore, the use of compressed air to propel or carry the mixtures is of proven efficiency and is particularly convenient due to the ready availability of a compressed air supply at most job sites.
The function and operation of typical spray gun designs involves the gradual introduction of the material to be sprayed into a stream of fast moving air. A characteristic design is illustrated in Roche U.S. Pat. No. 3,003,704 and McRitchie U.S. Pat. No. 3,236,459 where material drains from the device through an orifice centered about a nozzle emitting a jet of air. Contact with the jet causes the escaping material to be accelerated and transported towards the target surface. A variation of this design is illustrated in Roche U.S. Pat. No. 2,656,217 wherein the material issues from a nozzle centrally disposed within a stream of air. The air pressure, air volume, orifice size, nozzle shape and diameter and the location of the orifice relative to the nozzle are all factors that intimately effect the spray pattern and volume of the material issuing from the spray gun, as well as the coverage rate and texture of the resulting work product.
Many of the disadvantages associated with the prior art spraying devices are inherent in their typically complex designs and constructions. A device that relies on the interaction of a multitude of intricate parts in intricate configurations is initially expensive, is susceptible to failure or gradual deterioration in performance, and eventually requires costly or time consuming repairs. A further disadvantage of some prior art spraying devices is that the interior or a portion of the interior of the spray gun body is subjected to the force of the pressurized air. This limits the types of materials that can be used in the spray gun body's construction, requires either a precise casting or machining of the gun body and requires the utilization of extra seals and/or gaskets in its assembly.